Monday 19 August 2013

Delusion in DSM-5: A Response to Lisa


Kengo Miyazono
This post is a response to Lisa's earlier post on delusion in DSM-5.

Is the definition of delusion really different between DSM-5 and DSM-IV?

In DSM-5, definitional remarks on delusion appear twice; first, in "Schizophrenia Spectrum and Other Psychotic Disorders" in Section II (p.87) and, second, in "Glossary of Technical Terms" in Appendix (p.819). So, we need to look at both of them and compare them to their counterparts in DSM-IV.  


Let us begin with "Glossary", which is usually taken to be giving the official definition by DSM. 

A false belief based on incorrect inference about external reality that is firmly held despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not ordinarily accepted by other members of the persons's culture or subculture (i.e., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility. Delusional conviction can sometimes be inferred from an overvalued idea (in which case the individual has an unreasonable belief or idea but does not hold it as firmly as is the case with a delusion). (DSM-5, p.819) 


A false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person's culture or subculture (e.g., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility. Delusional conviction occurs on a continuum and can sometimes be inferred from an individual's behavior. It is often difficult to distinguish between a delusion and an overvalued idea (in which case the individual has an unreasonable belief or idea but does not hold it as firmly as is the case with a delusion). (DSM-IV, p.765) (p.821 in DSM-IV-TR)

Although some changes have been made in the last part of the quotes, they don't seem to be very different.  Especially, no changes have been made in response to the problems repeatedly raised for the definition in DSM-IV; delusions do not have to be "false", that delusions do not have to be "about external reality", delusions might not be "based on incorrect inference", and so on.   


Let us move on to "Schizophrenia Spectrum and Other Psychotic Disorders". 


Delusions are fixed beliefs that are not amenable to change in light of conflicting evidence. Their content may include a variety of themes (e.g. persecutory, referential, somatic, religious, grandiose). Persecutory delusions (i.e., belief that one is going to be harmed, harassed, and so forth by an individual, organization, or other group) are most common. Referential delusions (i.e., the belief that certain gestures, comments, environmental cues, and so forth are directed at oneself) are also common. Grandiose delusions (i.e., when an individual believes that he or she has exceptional abilities, wealth, or fame) and erotomanic delusions (i.e., when an individual believes falsely that another person is in love with him or her) are also seen. Nihilistic delusions involve the conviction that a major catastrophe will occur, and somatic delusions focus on preoccupations regarding health and organ function. (DSM-5, p.87)


Delusions (Criterion A1) are erroneous beliefs that usually involve a misinterpretation of perceptions or experiences. Their content may include a variety of themes (e.g., persecutory, referential, somatic, religious, or grandiose). Persecutory delusions are most common; the person believes he or she is being tormented, followed, tricked, spied on, or subjected to ridicule. Referential delusions are also common; the person believes that certain gestures, comments, passages from books, newspapers, song lyrics, or other environmental cues are specifically directed at him or her. The distinction between a delusion and a strongly held idea is sometimes difficult to make and depends on the degree of conviction with which the belief is held despite clear contradictory evidence. (DSM-IV, p.275) (DSM-IV-TR (p.299) is almost the same)


My impression is that they are, again, not very different overall. 


One difference is that DSM-IV says that delusions are "erroneous beliefs", while DSM-5 says that they are "fixed beliefs". This would be a nice change, because "erroneous" probably implies "false", but delusions do not have to be false. 

Another difference is that DSM-IV says that delusions involve a misinterpretation of perceptions or experience. This "empiricist" commitment is removed in DSM-5. This might be a good thing, because people might want DSM to be independent from theoretical issues like empiricism. 


Lisa says that DSM-5 narrows the gap between delusions and other irrational beliefs. But, this is not obvious. The change from "erroneous belief" to "fixed belief" doesn't seem to narrow the gap between delusions and other irrational beliefs. Again, eliminating empiricism doesn't seem to narrow the gap. Lisa might think that the following sentence in DSM-5, which comes in the paragraph following the one quoted above, narrows the gap.
 
"The distinction between a delusion and a strongly held idea is sometimes difficult to make and depends in part on the degree of conviction with which the belief is held despite clear and reasonable contradictory evidence regarding its veracity." (DSM-5, p.87)

But, actually, the last sentence of the quote from DSM-IV above says almost the same thing. 
Also, it is not obvious that the "strongly held idea" in the sentence includes everyday irrational beliefs that Lisa is talking about.

Summing up, although there are some minor changes between DSM-5 and DSM-IV, including some good ones, they are not remarkably different. Especially, no changes have been made in "Glossary" in response to the problems that have been raised for DSM-IV... 

5 comments:

  1. Hi Kengo and many thanks for this.

    You're right that I should have compared definitions of delusions as they appear in the description of schizophrenia (those that appear in the glossary do not differ).

    The definitions provided in the schizophrenia section are different from one another in the way you discuss (no mention of delusions needing to be false or to be due to a misinterpretation of experience in DSM-5). The fact that the definition of delusions in the DSM-5 glossary doesn't reflect these changes is puzzling to me, especially as it wouldn't have taken long to make the two definitions of delusions in the DSM-5 more consistent with one another.

    There is a sense in which the gap between delusions and other irrational beliefs is narrowed if an irrational belief needs to satisfy fewer conditions to count as a delusion - but I agree this is kind of weak.

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    1. Hi Lisa,

      Thanks for you comment!

      I think you are right. It is certainly puzzling that there is no remarkable change in the definition in glossary.

      I also agree that the definition in glossary and the description of schizophrenia are not very consistent with each other.

      The main problem of the definition in glossary seems to be that it is too strong. It excludes the delusions that are false, the delusions that are not based on inference, the delusions that are not about external reality, etc. On the other hand, the description of schizophrenia in DSM-5 seems to be too weak. It includes many non-delusional beliefs. For instance, non-delusional racism beliefs are presumably "fixed" and "not amenable to change in light of conflict evidence". (In this sense, I agree that DSM-5 narrows the gap between delusions and non-delusional irrational beliefs. But, this narrowing makes the definition too weak.) So, it seems to me that the right definition of delusion is somewhere between these two...

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    2. Sorry, I wanted to say that glossary excludes the delusions that are TRUE.

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  2. If you look at p. 87 of DSM-5 you'll see a section on Delusions. This is almost entirely a description of various kinds of delusion. Only a single sentence says anything relevant to defining delusion: "Delusions are fixed beliefs that are not amenable to change in the light of conflicting evidence".

    A completely different definition is offered on page 819 (in the Glossary of Technical Terms). Here we find that for something to count as a delusion, it has to be (a) a false belief based on incorrect differences about external reality and (c) held despite the existence of incontrovertible counter-evidence and (c) not held by other members of one's culture. As in DSM-IV.

    Since these definition are so contradictory (e.g one requires that delusional beliefs must be false and the other doesn't), there is no DSM-V definition of delusion.

    But does that matter? It would only matter if we were trying to make scientific or intellectual use of what DSM-V says about definitions; and DSM-V and DSM-IV are not fit for such purposes. So I don't see that readers of this blog should care about this at all

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    Replies
    1. Thanks for the comment!

      I agree that the definitions of delusion in DSM-5 are not very consistent with each other.

      Also, as you suggested, the lack of definition might not be a very serious problem for DSM-5.

      Still, it would be a good thing to think about various attempts (not just DSM) to define delusions. It might turn out that defining delusion is very difficult after all. Still, we will be able to learn something from knowing why delusions can't easily be defined.

      Here is an example. There is no accepted definition of "knowledge" in philosophy. But, knowing the reason why simple definitions of knowledge don't work helps us to understand what knowledge actually is. For instance, knowledge can't simply be defined as justified true belief because of so-called Gettier cases, the cases where justified true beliefs are achieved by luck. Thinking about these issues, I think, helps us to understand knowledge better, even though we don't have a good alternative definition of knowledge.

      The same thing might be true about the definition of delusion. The definitions of delusion in DSM are problematic. Still, we might be able to understand delusion better by looking at why these definitions are problematic.

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